It has been established that alkylpyrazines are natural components of tobacco smoke, and that they are contributors to tobacco smoke flavor [A. Baggett et al J. Chromatog. 97, 79 (1974)]. 2-Isopropenylpyrazine has been identified as a tobacco flavorant constituent of burley tobacco [E. Demole et al, Helv. Chem. Acta, 55, 1866 (1972)].
Patents which disclose the addition of various pyrazine compounds to tobacco and foodstuffs as a means of providing flavor or flavor enhancement include U.S. Pat. Nos. 3,684,809; 3,705,158; 3,754,934; 3,764,349; 3,767,426; and 3,881,025.
It is characteristic of pyrazine and pyridine and other heteroaromatic derivatives employed as tobacco flavorants in the prior art that the respective derivatives have the disadvantage of both high volatility and low odor threshold. Both of these properties significantly restrict the extent that these heteroaromatic derivatives can be utilized as flavorants in tobacco compositions. A quantity of a pyrazine or pyridine derivative in a tobacco composition sufficient to have a noticeable effect in low delivery cigarettes causes a marked pack aroma.
U.S. Pat. No. 4,259,969 endeavors to overcome some of the disadvantages of the above-described flavorant technology. The patent describes smoking composition flavorant-release additives which are not volatile at ambient temperatures, such as 2-(2-hydroxy-2-phenylethyl)-3,5,6-trimethylpyrazine and related derivatives corresponding to the formula: ##STR3## wherein X is selected from pyrazine and pyridine radicals corresponding to the chemical structures: ##STR4## where R is hydrogen or methyl; R.sup.1 is hydrogen or C.sub.1 -C.sub.10 alkyl; R.sup.2 is a substituent selected from aliphatic, alicyclic and aromatic groups containing about 1-12 carbon atoms; and R.sup.1 and R.sup.2 when taken together with connecting elements form an alicyclic structure.
Other smoking composition developments of interest with respect to the present invention are those in which an organic additive is utilized that releases at least two flavorants which are organoleptically compatible, and enhance the flavor and aroma of cigarette smoke.
U.S. Pat. Nos. 4,036,237; 4,141,906; and 4,178,458 describe .beta.-hydroxyesters which as additives in smoking compositions pyrolyze into volatile aldehyde and ester flavorants under smoking conditions.
U.S. Pat. Nos. 4,473,085 and 4,607,118 describe .beta.-hydroxyesters which as additives in smoking compositions pyrolyze into volatile ketone and ester flavorants under smoking conditions.
U.S. Pat. No. 4,312,368 describes smoking compositions which contain a heterocyclic-hydroxy-substituted carboxylate flavorant-release additive such as ethyl 2-(2-butyl)-3-hydroxy-3-methyl-3--(3-pyridyl)propionate. Under smoking conditions this additive pyrolyzes into 3-acetylpyridine and ethyl .beta.-methylvalerate flavorants.
There is continuing research effort to develop improved smoking compositions which generate smoke with flavorant-enhanced taste and character under smoking conditions.
Accordingly, it is an object of this invention to provide smoking compositions having incorporated therein a flavorant component which is characterized by lack of mobility and/or volatility at ambient temperature.
It is another object of this invention to provide smoking compositions having incorporated therein a flavorant-release additive which under normal smoking conditions imparts improved flavor to mainstream smoke and improved aroma to sidestream smoke.
It is a further object of this invention to provide novel organic compounds which are adapted to be incorporated into cigarette fillers and/or paper wrappers, and which under normal smoking conditions release volatile pyrazine and cinnamaldehyde type flavorant constituents into cigarette smoke.
Other objects and advantages of the present invention shall become apparent from the following description and examples.